Here's an interesting fact about weather in Japan: seasons are marked and usually follow quite a "rigorous" pace. It's possible to define clear periods more or less favorable to travel, for example in the Kanto area: sakura (cherry blossoms) the first week of April, momiji (maple leaves) the second half of November, or the great heat of summer between mid-July and late August.
In this calendar, another characteristic period should not be forgotten: tsuyu 梅雨, literally "plum rain," which is what one might call rainy season. Japan is not one of those countries with a monsoon, but during these six weeks, rain pours more than during the rest of the year. Not necessarily every day, but if you are planning a trip with a lot of outside visits, it has to be taken into account. Humidity greatly increases to reach its summer level. At this time, cockroaches also reappear in Japan!
According to the Japan Meteorological Agency, tsuyu season (also known as baiyu) takes place between these dates:
- Tokyo area: from June 8 to July 20
- Kansai / Kinki (Kyoto, Osaka...): from June 6 to July 19
- Shikoku: from June 4 to July 17
- Kyushu: from May 29 to July 13
- Okinawa: from May 8 to June 23
Note that Hokkaido is the only one not to be affected by tsuyu. A second rainy season, significantly less intense, also exists in Japan between mid-September and early October: it's called Akisame 秋雨, ie the "autumn rain."
Rainy seasons are not necessarily the most profitable to travel to Japan, but if this is your only available period, it's still possible to enjoy your stay. First, make good use of umbrellas, quite a Japanese institution! Then, target your indoor visits (museums, shopping arcades, department stores...) and visit regions that revel in moisture, such as Mount Koya or Yakushima.